1. Field of the Invention
The present invention relates to a an information processing device, a laser irradiation device, a drawing information generating method, a control system, and a program for generating drawing information for drawing a line image such as a character contiguously or discontiguously.
2. Description of the Related Art
A heat sensitive paper is sometimes used as a label for printing an address of an article or a name of an article. For example, such a heat sensitive label is attached to a plastic container used in a factory. The heat sensitive label has a property of changing color by heat and allows for writing of characters and symbols by using a thermal head or the like.
A rewritable type of such a heat sensitive label which can be written or erased repeatedly is now appearing. When used for commodity distribution, it is desirable to write or erase a label while being attached to a container. Thus, a method for drawing characters or the like by irradiating a label with a laser contiguously and heating the label has been proposed (see Patent Document 1 for example). The Patent Document 1 discloses a relay lens system transferring an image formed by a laser which comes from one end of a plurality of lens systems consisting of flexible joints, to the other end.
In addition, an image formation by a laser is known in the prior art (see Patent Document 2 for example). The Patent Document 2 discloses an image forming method which divides a single original image datum into a plurality of lines and irradiates a photoconductive drum with a laser with respect to each line.
Generally, a beam diameter of a laser is at least about 0.3 mm. Due to its relatively large beam diameter, a laser is often used with a stroke font for drawing characters or the like. That is, it is not necessary to specify an outline and fill in area within the outline as with an outline font commonly used for drawing characters or the like. The stroke font allows a character to be drawn just like writing a character in pencil by scanning a laser along coordinates defined by core line data of characters. If a change of a size of a character to be drawn is desired, coordinates of the original font datum are enlarged or reduced, a piece of drawing information for the character is newly generated, a rewritable medium is scanned by the laser along the coordinates, and the character is drawn.
However, due to limitations to a lower limit of a beam diameter of a laser beam (about 0.3 mm), there is a disadvantage in that writing a small sized character becomes difficult. That is, due to the thickness of a line to be drawn, it becomes difficult to discern crushed characters if drawn characters are small. If the line is like a very fine line drawn by a laser beam used in a laser printer, the line does not produce a crushed character even if the character is drawn by the stroke font in so far as the character has a size discernible by human. However, since a line drawn by a laser beam used for producing a change in color of a thermal rewritable medium is thick, in the case of complicated characters such as Chinese characters, it often becomes difficult to discern the characters, without 5-millimeters-square-size or so, due to an overlap between adjacent lines.
In a commonly-used printer or word processor software, a method for switching fonts according to a character size is known (see Patent Documents 3 and 4 for example). In printing or displaying a rather small character, the software prevents reduction of visibility by using a small-sized font datum for the same character.
Also, a printer which draws a character of any size by omitting a stroke, in rasterizing an outline font datum, if a line width of the stroke is less than or equal to a predetermined value, is disclosed (see Patent Document 5 for example).
However, since a line drawn by a laser used in a laser printer is very thin, drawing an outline by an outline font and filling in area with the outline is still a principal method. There is no technology which has devised a drawing method by a stroke font for the case of drawing a small sized character.
Now, in Patent Documents 3 and 4, a decision whether or not to use a small-sized font datum for drawing a small sized character is based only on a character size. However, for example, comparing the case of a line thickness of 0.3 millimeter and the case of a line thickness of 0.6 millimeter, even if the same character with the same size is drawn, the latter is more likely to be crushed (being “crushed” means “becoming unreadable due to overlaps between strokes of the character”). Thus, in the stroke font, it is difficult to decide whether or not to use a small-sized font datum based only on the character size.
That is, as described in Patent Documents 3 and 4, it is impossible to handle the stroke font simply by switching pieces of drawing information depending on a character size. In laser printer, since a line to be drawn is very thin and its drawing method is different from a drawing method of the stroke font, there is no need to consider a character thickness. Thus, it is impossible to apply technology of the laser printer to the drawing by the stroke font without change.
Moreover, in a printer described in Patent Document 5, if a rasterized stroke is thin, the printer omits the stroke. However, Patent Document 5 does not disclose improving visibility of a character in the case where a character drawn by a laser is thick.
In view of the above-mentioned problems, it is an object of the present invention to provide an information device, a laser irradiation device, a drawing information generating method, a control system, and a program, each of which draws a small sized character visibly by choosing a font datum appropriately even if a character size and a thickness of a line drawn by a laser are variable.
Patent Document 1: JP-A-2004-090026
Patent Document 2: JP-A-2004-341373
Patent Document 3: JP-A-2007-152580
Patent Document 4: JP-A-2008-219793
Patent Document 5: JP Patent 3146771